Low levels of genetic diversity detected by RAPD analysis in geographically distinct accessions of Bacopa monnieri

Brahmi (Bacopa monnieri) is atraditional Indian medicinal plant known for its natural nootropicaction of saponins present in large amount in its shoots. Acollection of 24 B.monnieri accessions from differentagro-climatic zones of India and an introduction from Malaysiamaintained in the field genebank at CIMAP was analysed for RAPDvariation. Among the 40 random primers tested, 29 primers generatedone or more polymorphic bands. The number of polymorphic bandsgenerated was primer dependent, ranging from 2 to maximum of 8.Similarity matrices were generated from the RAPD data on the basis ofNei's estimates of similarity indices and dendrograms wereconstructed based on UPGMA clustering. All the accessions were foundto be in the range of 0.8–1.0 of similarity, which isindicative of a narrow genetic base among the various accessions witha medium level of polymorphism. It was possible to differentiateindividual accessions, showing differences in morphological andgrowth properties at DNA level. The observed low levels of geneticvariation were attributed to interplay of sexual and vegetative modesof reproduction and similarity of local environments in habitats ofB. monnieri.